Technical Field
The present invention relates to a memory control circuit unit for controlling a rewritable non-volatile memory module, a memory storage apparatus using the memory control circuit unit, and a data accessing method thereof.
Description of Related Art
The growth of digital cameras, mobile phones, and MP3 players has been expanded rapidly in recent years. Consequently, the consumers' demand for storage media has increased tremendously. A rewritable non-volatile memory is one of the most adaptable memories for portable electronic products such as notebook computers due to its data non-volatility, low power consumption, small volume, non-mechanical structure and high read/write speed. A solid state drive is a storage apparatus which utilizes a flash memory as its storage medium. For these reasons, the flash memory has become an import part of the electronic industries.
With advancements in the semiconductor fabrication, a flash memory module having a memory cell capable of storing a plurality data bits has been developed in the current technology. Specifically, a data writing (or known as programming) of the flash memory module changes on-state of a channel of the memory cell in order to present different storage states by applying a voltage to a specific terminal of a flash memory device (e.g., amount of electrons in an charge-trapping layer of a gate may be changed by controlling a gate voltage). Take a Multi-Level Cell (MLC) NAND type flash memory for example, when a lower page data is 1 and an upper page data is 1, a control circuit may control a word line control circuit not to change the gate voltage in the memory cell but maintain the storage state of the memory cell at “11”; when the lower page data is 1 and the upper page data is 0, the word line control circuit changes the gate voltage in the memory cell under control of the control circuit, so as to change the storage state of the memory cell to be “10”; when the lower page data is 0 and the upper page data is 0, the word line control circuit changes the gate voltage in the memory cell under control of the control circuit, so as to change the storage state of the memory cell to be “00,” and, when the lower page data is 0 and the upper page data is 1, the word line control circuit changes the gate voltage in the memory cell under control of the control circuit, so as to change the storage state of the memory cell to be “01.” In other words, when data is read, the control circuit identifies the storage state of a current memory cell according to the gate voltage in the current memory cell.
However, in such architecture where one memory cell is capable of storing multiple bits, if data stored on the memory cells of the same word line is not disarranged properly, errors may occur on the data identification due to factors such as uneven arrangement, shifts in reading voltage or uneven resistance on bit lines. Accordingly, it is one of the major subjects in the industry as how to effectively disarrange the written data when executing a programming operation on the rewritable non-volatile memory module.
Nothing herein should be construed as an admission of knowledge in the prior art of any portion of the present invention. Furthermore, citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention, or that any reference forms a part of the common general knowledge in the art.